Microtome assemblies

ABSTRACT

A microtome assembly comprises a pivotally suspended knife assembly and knife displacing means which are coupled to the knife assembly such that forward movement of the displacing means urges the knife assembly into a lower position before horizontal displacement of the knife assembly on its cutting stroke, and retractive movement of the displacing means urges the knife assembly to an upper position before horizontal displacement of the knife assembly on its return stroke. The knife body is therefore lifted clear of a specimen before its return stroke thereby avoiding damage to a cut surface of the specimen.

I O United States Patent [151 3,673,904 Cooper et al. July 4, 1972MICROTOME ASSEMBLIES References Cited [72] Inventors: Michael l-lenryCooper, Bumley; Leslie UNITED STATES PATENTS Alva y Accringwn, both ofEngland 3,462,969 8/1969 Grasenick et al ..s3/915.5 x 73 A eN.G.N.L'mited M rfl t,H ll,Y kh' l 1 sslgn 6 England I a ee u or S IrePrimary Examiner-James M. Meister AttorneyScrivener, Parker, Scrivener &Clarke [22] Filed: Dec. 14, 1970 [57] ABSTRACT PP NO-I 97,536 Amicrotome assembly comprises a pivotally suspended knife assembly andknife displacing means which are coupled to the [30] Foreign Applicationi i Data knife assembly such that forward movement of the displacingmeans urges the knife assembly into a lower position before Dec. 16,1969 Great Britain ..6l,267/69 horizontal displacement of the knifeassembly on is cutting stroke, and retractive movement of the displacingmeans urges the knife assembly to an upper position before horizontaldis- [52] US. Cl ..83/171,gggpggiggkff placement of the knife assemblyon 8 return stroke The knife [51] lm Cl 1/06 body is therefore liftedclear of a specimen before its return [58] Fieid stroke thereby avoidingdamage to a cut surface of the 90/31, Specimen 9 Claims, 5 DrawingFigures PATENTEDJUL 4 I972 3. 673.904

snanlor t n'f 1m M 20 24 I 16 34 163-0 1825 I PAT ENTEDJUL 419. 2 3,673,904 SHEET 2 0F 3 FIG.3.

PATENTEDJUL 4|972 3,573,904

SHEET 30F 3 FIG.Q4.

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MICROTOME ASSEMBLIES This invention relates to rnicrotome assembliesparticularly for use in freeze etching equipment used in preparingspecimens for electron-microscopical investigations.

According to the present invention a microtome assembly comprises aheight adjusting device, a suspension arm which is attached thereto by afriction bearing and which carries a knife assembly, and knifedisplacing means pivotally attached to the knife assembly such thatforward movement of the displacing means urges the knifeassembly into alower position before horizontal displacement thereof takes place andretractive movement urges the knife assembly to an upper position beforea return horizontal displacement takes place. The knife assemblypreferably comprises two blades spaced horizontally relative to eachother, which blades may also be spaced vertically relative to eachother. A stop means is preferably provided limiting the extent of themovement of the knife assembly between theupper and lower positions. Theknife assembly preferably also comprises means for adjusting the angleat which the knife, i.e. the cutting blade, is presented to thespecimen.

The invention will now be described by way of example with reference tothe accompanying drawings of which:

FIG. 1 shows a side elevation of part of a rnicrotome assemblyconstructed in accordance with one embodiment of the invention;

FIG. 2 shows an enlarged detail of a knife assembly;

FIG. 3 shows a front elevation of the knife assembly;

FIG. 4 shows an enlarged detail of a knife assembly according to asecond embodiment; and

FIG. 5 is a section on the line V-V of FIG. 4.

In the drawings a height adjusting device comprising a sup port columnslidable in a base plate 11 extends into a vacuum chamber 12 and carriesa suspension arm 13 pivotally attached to it by a friction bearing14.'The bearing is arranged to be vertically over a specimen 15 which isto be cut by the rnicrotome assembly. The suspension arm 13 incorporatesa thermally non-conductive section, made for example of PER- SPEX(Registered Trade Mark), which is not shown in the drawings.

To the lower end of the suspension arm 13 is rigidly attached a hollowknife body 16 through which a low temperature fluid, e.g. liquidnitrogen, is passed. A cutter head 18 is attached to the knife body by afreely rotatable pivot 20. Two cutter blades 22 and 23 are clamped tothe cutter head by clamps 24 and 25 in such positions that the cuttingedge 26 of the blade 22 is slightly lower than the cutting edge 28 ofthe blade 23. j

The cutting blades are cooled by thermal conductivity through the pivot20, and the cooling is supplemented by a flexible link of materialhaving a high thermal conductivity, e.g. the copper braid shown at 30,between the knife body 16 and the cutter head 18.

A clamping pillar or plate 32 is rigidly attached to the cutter head 18and adjacent to it is a stop plate 34. The stop plate and clamping plateare clamped together by a screw 36 which passes through an arcuate slot38 in the stop plate and engages in a tapped hole in the clamping plate.The screw 36 may be loosened to permit angular adjustment of the stopplate and clamping plate relative to each other, thereby determining theangle between the cutter blades 22 and 23 and the knife body 16 and thusthe angle at which the blades are presented to the specimen.

A knife displacing means in the form of a rod 40, displaceable by, forexample, a solenoid assembly which is not shown, is pivotally connectedat 42 to the stop plate 34 by a clevis 44.

The knife body 16 has an upwardly projecting portion 46 carrying ahorizontally extending plate 48. A pin or dowel 50 rigidly secured tothe stop plate 34 engages in a slot 52 in the plate 48. The slot is ofgreater width than the pin, thus permitting relative movement betweenthe cutter head assembly comprising the pin 50 itself, stop plate 34,clamping plate 32 and cutter head 18 on the one hand and the knife body16 on the other.

When the rod 40 is displaced forwardly i.e. from left to right in FIG.2, the cutter head assembly is rotated about the pivot 20 as far as theclearance between the pin 50 and slot 52 permits, thereby lowering thecutter blades 22 and 23. While this rotation of the cutter head assemblyis taking place, the friction caused by the friction bearing 14 betweenthe suspension arm 13 and the height adjusting column 10 prevents theknife assembly from moving forward. When the pin 50 comes up against theside of the slot 52 the whole knife assembly is then horizontallydisplaced sufiiciently for one of the cutting blades to make a cutthrough the specimen. When the retractive movement of the spindlebegins, the cutter blades are raised as the cutter head is rotated backagain about the pivot 20, the friction bearing 14 again preventing thereturn horizontal displacement of the knife assembly from beginninguntil the pin 50 has moved across to the other side of the slot 52. Thusthe cutting blades move back on the return stroke at a level above thespecimen, thereby clearing the specimen and thus avoiding thepossibility of damaging the freshly cleaved face of the specimen whichpossibility would exist if the return stroke were to follow the samepath as the forward stroke particularly if ice particles had beendeposited on the face of the specimen behind the blade.

The adjustment of the angle of the cutting blades relative to thespecimen by means of the screw 36 and arcuate slot 38 enables the bladesto be set at the optimum angle for the particular material to becleaved.

Each cutting blade is used separately, the knife assembly beingdisplaced on each stroke only through a suflicient are about thefriction bearing 14 to permit the blade then operative to pass throughthe specimen. Two blades are incorporated so that if the sharp edge onthe first becomes blunt or damaged during the initial stages of themicrotoming when comparatively large cuts are being made, the secondblade may be brought into use for the final stages when smaller cuts arebeing made and the risk of damaging the cutting edge is correspondinglyreduced.

In the embodiment shown in FIGS. 4 and 5, the cutter head 118 is madehollow so that cooling medium such as liquid nitrogen may be circulateddirectly through the cutter head by way of pipes 116 which incorporatesflexible portions 117 to accommodate tilting and linear displacement ofthe cutter head during operation of the rnicrotome assembly.

Also shown in FIGS. 4 and 5 is one manner in which the cutting blades122, 123 are fixed in the cutter head. The blades 122, 123 are locatedin slots 124, 125 in the cutter head 118 and held in place by clampingplates 126, 127 urged against their respective blades by screws 128,129. The clamping plates 126, 127 are located by pegs 130 which passthrough apertures in the clamping plates so as to be retained within theslots whilst being freely displaceable by the screws. When the screwsare tightened, the clamping plates clamp the blades firmly against thelower walls of the slots thus ensuring good thermal contact between theblades and the cutter head.

The term "friction bearing" used herein means a bearing which inhibitsrotau'on of the members which it connects. This may be achieved bymaking the bearing surfaces of materials having a high coefficient offriction, for example, or by loading it e.g. with a threaded nut and/ora spring.

We claim:

1. A rnicrotome assembly comprising a base member, a support columnslidable through said base member, a suspension arm pivotally attachedat one of its ends to said support column, a friction bearing betweensaid support column and said suspension arm, a knife assembly pivotallyattached to the other end of said suspension arm and knife displacingmeans pivotally attached to said knife assembly, said knife displacingmeans including means operable to urge said knife assembly into a lowerposition before horizontal displacement of said knife assembly byforward movement of said knife displacing means and to urge said knifeinto an upper position before return horizontal displacement of saidknife assembly by retractive movement of said knife displacing means.

2. A microtome assembly according to claim 1, wherein said knifeassembly comprises a knife body and a cutter head, said cutter headbeing coupled to said knife displacing means and being pivotablerelative to said knife body, a lost-motion connection being providedbetween said knife body and said cutter head such that initial forwardand retractive movement of said knife displacing means causes tilting ofsaid cutter head relatively to said knife body.

3. A microtome assembly according to claim 2. wherein said lost-motionconnection comprises a pin able to be fixed relative to said cutter headand means defining a slot in a part of said knife body, said pin passingthrough said slot and having a width less than that of said slot.

4. A microtome assembly according to claim 3 wherein a stop plate ispivotably attached said cutter head and carries said pin, and includingclamping means to releasably clamp said stop plate to said cutter head.

5. A microtome assembly according to claim 4 wherein said cutter headincludes a clamping plate lying adjacent said stop plate and whereinsaid clamping means comprises means defining an arcuate slot in saidstop plate, means defining a threaded bore in said clamping plate and ascrew passing through said arcuate slot and engaging in said threadedbore.

6. A microtome assembly according to claim 2 wherein said knife assemblycarries two blades.

7. A microtome assembly according to claim 4 wherein said knife assemblycarries two blades.

8. A microtome assembly according to claim 2 wherein said knife body ishollow and includes means to enable cooling fluid to be passed throughsaid knife body.

9. A microtome assembly according to claim 2 wherein said cutter head ishollow and includes means to enable cooling fluid to be passed throughsaid cutter head.

1. A microtome assembly comprising a base member, a support columnslidable through said base member, a suspension arm pivotally attachedat one of its ends to said support column, a friction bearing betweensaid support column and said suspension arm, a knife assembly pivotallyattached to the other end of said suspension arm and knife displacingmeans pivotally attached to said knife assembly, said knife displacingmeans including means operable to urge said knife assembly into a lowerposition before horizontal displacement of said knife assembly byforward movement of said knife displacing means and to urge said knifeinto an upper position before return horizontal displacement of saidknife assembly by retractive movement of said knife displacing means. 2.A microtome assembly according to claim 1, wherein said knife assemblycomprises a knife body and a cutter head, said cutter head being coupledto said knife displacing means and being pivotable relative to saidknife body, a lost-motion connection being provided between said knifebody and said cutter head such that initial forward and retractivemovement of said knife displacing means causes tilting of said cutterhead relatively to said knife body.
 3. A microtome assembly according toclaim 2 wherein said lost-motion connection comprises a pin able to befixed relative to said cutter head and means defining a slot in a partof said knife body, said pin passing through said slot and having awidth less than that of said slot.
 4. A microtome assembly according toclaim 3 wherein a stop plate is pivotably attached said cutter head andcarries said pin, and including clamping means to releasably clamp saidstop plate to said cutter head.
 5. A microtome assembly according toclaim 4 wherein said cutter head includes a clamping plate lyingadjacent said stop plate and wherein said clamping means comprises meansdefining an arcuate slot in said stop plate, means defining a threadedbore in said clamping plate and a screw passing through said arcuateslot and engaging in said threaded bore.
 6. A microtome assemblyaccording to claim 2 wherein said knife assembly carries two blades. 7.A microtome assembly according to claim 4 wherein said knife assemblycarries two blades.
 8. A microtome assembly according to claim 2 whereinsaid knife body is hollow and includes means to enable cooling fluid tobe passed through said knife body.
 9. A microtome assembly according toclaim 2 wherein said cutter head is hollow and includes means to enablecooling fluid to be passed through said cutter head.